Unite said staff turned up for work at Trade Manufacturing Facility (TMF) of Newtown last week but were told the company had stopped trading.
Administrators Smith and Williamson have been instructed to place the company into voluntary liquidation.
Howard Wright, of Unite in Newtown, told the BBC: “The staff turned up for work as normal on 18 October to be told there was no work, and the shutters were coming down and the company was to cease trading.
“The workers have been made redundant. People are still waiting for wages from the last couple of weeks.”
A union meeting with the redundant workers will be held this afternoon.
A Smith and Williamson spokeswoman confirmed that TMF stopped trading on 18 October and the workforce was dismissed by the “principal director”.
She said the director instructed Smith and Williamson “to assist to liquidate the company”, and statutory meetings of company members and creditors was likely to take place on the 25 November.
She added that these meetings would place TMF in creditors’ voluntary liquidation, and would appoint the liquidator.
Smith and Williamson said it was not yet known how many people TMF employed. It is presently aware of 31 staff, but said there might be 38.